1. Field of the Invention
The present invention relates to an optical device for increasing the visual field of view of a person suffering from Homonymous Hemianopsia which is a loss of part of the visual field while the remaining part of the visual field is normal or correctable with eyeglasses. Homonymous Hemianopsia is generally the loss of one-half of a visual field wherein both eyes are affected. Homonymous Hemianopsia is a condition which may result from a number of catastrophic occurrences such as stroke, brain tumor or lesions in the brain. The visual field defect is called congruous when the visual defect or loss of visual field is exactly the same for both eyes and incongruous when there are differences between both eyes. Many people with Homonymous Hemianopsia are not aware of this visual disability since they manage to compensate by employing abrupt eye movements to the hemianopic side, fixate excessively towards the hemianopic side or move the head from side to side. Hemianopsia is usually absolute and when homonymous, the same side of both eyes is affected.
2. Prior Art
Attempts have been made in the past to provide Homonymous Hemianopsia corrective devices to increase the overall field of view over the limited angular field of view of uncorrected vision of a person suffering from Homonymous Hemianopsia. One such prior art device includes first and second space reflectors disposed in front of one of the two eyes of a person suffering from Homonymous Hemianopsia. The first and second reflectors block the direct field of view of the one eye and substitute in its place a virtual image of an additional angle of sight as more fully described in U.S. Pat. No. 4,155,633 entitled "Corrective Optical Device for Homonymous Hemianopsia" issued to Jerold J. Benavie. Other attempt include a dental mirror connected to a pair of eyeglasses to observe laterally disposed objects with the mirror.
None of the aforesaid prior art attempts and no other means are known to the applicant to utilize an optical device which increases the lateral view of a person having Homonymous Hemianopsia with minimum obstruction of the forward visual field, is inexpensive to manufacture, light in weight, easy to use and extends the lateral view without loss of the front view.